As this type of liquid supply, conventionally, there is a generally known one in which a rotating cam mechanism provided in an outer shaft is used to cause a tip end supplying portion to protrude from and retract into the outer barrel. For protrusion and retraction of the tip end supplying portion, a known rotating cam mechanism consisting of a rotating cam, a knock member, and a cam main body is used in general. The rotating cam mechanism can carry out switching operation in which the rotating cam rotates a predetermined angle every time the knock member presses the rotating cam to move alternately between a front position and a back position. When the rotating cam is in the front position, the tip end supplying portion protrudes from a tip end of the outer shaft. When the rotating cam is in the back position, the tip end supplying portion retracts into the outer shaft.
A structure for smoothly supplying a liquid by pressurizing action synchronized with actuation of the above-mentioned rotating cam mechanism is proposed in each of Patent Documents 1 to 6, for example.
In the structure proposed in each of Patent Documents 1 to 6, a pressurizing space which can communicate with an inside of a liquid housing tube is provided in the outer shaft and the pressurizing space is open to atmospheric pressure when the rotating cam is in the back position and becomes a pressurizing sealed space when the rotating cam is in the front position. Therefore, when the rotating cam moves to the front position to supply the liquid and the tip end supplying portion protrudes, the inside of the liquid housing tube is pressurized and it is possible to smoothly supply the liquid with the assistance of the pressurizing action.